An electron moving with a speed u along the positive x-axis at `y=0` enters a region of uniform magnetic field which exists to the right of y-axis. The electron exits from the region after some time with the speed v at coordinate y, then

Options

A. `v gt u , y lt 0`
B. `v = u, y gt 0`
C. `v gt u , y gt 0`
D. `v = u, y lt 0`

Answer

d

Explanation

Velocity of the electron is along X-axis. The direction of cross product of velocity and inward magnetic field is along positive Y-axis but the electron is a negative charge so it will experience force along negative Y-axis. Circular path of the electron will be on negative side of Y-axis. Besides, the speed of electron will not be affected by the magnetic field and hence option (d) is correct.